JAMB - Mathematics (2004 - No. 44)
PQRSTV is a regular polygon of side 7 cm inscribed in a circle. Find the circumference of the circle PQRSTV.
56 cm
22 cm
42 cm
44 cm
설명
| Each interior Angle of the polygon = | (n-2) | 180 |
| _n |
| = | (6-2) | 180 |
| _6 |
= 4 x 30
= 120o
i.e ∠PQR = 120o ∴ RQD = 120/2 = 60o also
∴ Δ QOR is equilateral Δ ∴ QO = 7cm
∴ PO = QO = RO ...... = 7cm radius of the circumference of the circle = 2πr
= 2 x 22/7 x 7/1
= 44 cm